1. Field of the Invention
The present invention relates to high-frequency front-end circuits that transmit and receive a plurality of communication signals having different communication schemes.
2. Description of the Related Art
To date, various high-frequency front-end circuits for transmitting and receiving a plurality of communication signals utilizing different frequency bands with a common antenna have been devised. FIG. 1 is a circuit configuration diagram of a typical high-frequency front-end circuit 10P of the related art. The high-frequency front-end circuit illustrated in FIG. 1 illustrates an example in which four different types of communication signals are transmitted and received using a common antenna.
The high-frequency front-end circuit 10P of the related art includes a switch device 11 and SAW duplexers 121, 122, 123 and 124. The switch device 11 has a common terminal PIC(ANT0) and individual terminals PIC(RF1) to (RF4). The switch device 11 is initiated by a driving voltage input from a driving power supply terminal PIC(VDD) and connects any one of the individual terminals PIC(RF1) to (RF4) to the common terminal PIC(ANT0) in accordance with a control signal input from any of a plurality of control signal input terminals PIC(Vc). A common antenna ANT is connected to the common terminal PIC(ANT0).
The SAW duplexer 121 is connected to the individual terminal PIC(RF1). A transmission filter of the SAW duplexer 121 is connected to a first transmission signal input terminal PM(Tx1). A reception filter of the SAW duplexer 121 is connected to a first reception signal output terminal PM(Rx1).
The SAW duplexer 122 is connected to the individual terminal PIC(RF2). A transmission filter of the SAW duplexer 122 is connected to a second transmission signal input terminal PM(Tx2). A reception filter of the SAW duplexer 122 is connected to a second reception signal output terminal PM(Rx2).
The SAW duplexer 123 is connected to the individual terminal PIC(RF3). A transmission filter of the SAW duplexer 123 is connected to a second transmission signal input terminal PM(Tx3). A reception filter of the SAW duplexer 123 is connected to a second reception signal output terminal PM(Rx3).
The SAW duplexer 124 is connected to the individual terminal PIC(RF4). A transmission filter of the SAW duplexer 124 is connected to a fourth transmission signal input terminal PM(Tx4). A reception filter of the SAW duplexer 124 is connected to a fourth reception signal output terminal PM(Rx4).
With such a configuration, the high-frequency front-end circuit of the related art transmits a transmission signal from each of the transmission signal input terminals from the common antenna ANT and outputs a reception signal received by the common antenna ANT from a desired reception signal output terminal.
Incidentally, currently, as examples of wireless communication schemes for cellular phones, in the third generation partnership project (3GPP) standards of third generation (3G) cellular phones, such as the wide band code division multiple access (W-CDMA) standard and the third generation project third generation 2 (3GPP2) standard, CDMA 2000 (wide band cdma one) is a frequency division duplex (FDD) scheme and global system for mobile communications (GSM) of the 3GPP standard, time division long term evolution (TD-LTE) and time division synchronous code division multiple access (TD-SCDMA) are time division duplex (TDD) schemes.
Therefore, a high-frequency front-end circuit that can handle communication signals of both the FDD scheme and the TDD scheme is needed and a high-frequency front-end circuit that transmits and receives FDD-scheme communication signals and TDD-scheme communication signals using a common antenna is described in Japanese Unexamined Patent Application Publication No. 8-316873 as an example of such a high-frequency front-end circuit.
The high-frequency front-end circuit described in Japanese Unexamined Patent Application Publication No. 8-316873 has one port that is used for FDD-scheme communication signals and two ports that are used for TDD-scheme communication signals as illustrated in FIG. 3 of Japanese Unexamined Patent Application Publication No. 8-316873 and the ports are switched between.
However, as has been described above, in the high-frequency front-end circuit of the related art, a multiple-branch switch device is used and a number of duplexers equal to the number of types of transmission and reception signals is needed in order to handle a plurality of communication signals (transmission and reception signals). Consequently, the scale of the circuit may be increased and it may be difficult to reduce the cost.
In addition, in the high-frequency front-end circuit of the related art described in Japanese Unexamined Patent Application Publication No. 8-316873, a path for a TDD-scheme communication signal and a path for an FDD-scheme communication signal need to be individually provided and the scale of the circuit is increased. In addition, since the transmission frequency band and the reception frequency band overlap for a TDD-scheme communication signal, in the high-frequency front-end circuit of the related art, it is not possible to use a duplexer that can be used for an FDD-scheme communication signal and therefore a switch device is necessary and as a result the circuit scale is increased and cost reduction is difficult also due to this point.